IPv4 Subnetting Practice Flashcards: Boundaries & Host Ranges

Question 1

In IPv4 CIDR notation, what does the /27 specify?

Accepted Answer

The first 27 bits are the network prefix. The remaining 32 − 27 = 5 bits identify positions within that address block.

Question 2

Which dotted-decimal IPv4 subnet mask matches /27?

Accepted Answer

255.255.255.224. The final octet is 11100000 in binary: three prefix bits after the first 24.

Question 3

How many total IPv4 addresses are in a /29 block, before excluding any addresses?

Accepted Answer

8 addresses. There are 32 − 29 = 3 host bits, so the block has 2^3 = 8 positions.

Question 4

To find an IPv4 network address from an address and prefix, what values must the host bits have?

Accepted Answer

All host bits must be zero. Keep the prefix bits unchanged; clearing the remaining bits gives the block’s first address.

Question 5

For an ordinary IPv4 LAN with a /24–/30 prefix, which two addresses are excluded from the traditional usable host count?

Accepted Answer

The network address and the subnet broadcast address. Traditional usable capacity is 2^(32 − prefix length) − 2; this rule is not the RFC 3021 /31 point-to-point rule.

Question 6

Which dotted-decimal IPv4 subnet mask matches /23?

Accepted Answer

255.255.254.0. Seven prefix bits in the third octet give 11111110; the fourth octet contains only host bits.

Question 7

What is the network address of 198.51.100.77/27?

Accepted Answer

198.51.100.64. The block has 32 addresses; 77 lies between the boundaries 64 and 96.

Question 8

What is the subnet broadcast address for an ordinary IPv4 LAN containing 203.0.113.149/28?

Accepted Answer

203.0.113.159. This block starts at .144; the next starts at .160, so the broadcast is one address before .160.

Question 9

What is the first traditionally usable host address in the ordinary IPv4 LAN containing 192.0.2.174/26?

Accepted Answer

192.0.2.129. The network address is .128; the first host is the next address.

Question 10

An ordinary IPv4 LAN needs 6 interface addresses in total, including its gateway. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

Accepted Answer

/29. Its 8 total addresses leave 6 traditional host addresses. A /30 leaves only 2.

Question 11

On an ordinary IPv4 LAN, is 198.51.100.127/27 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Subnet broadcast address. The block runs from .96 through .127; .127 has every host bit set to one.

Question 12

A learner says an ordinary IPv4 /25 LAN has 128 traditionally usable host addresses. What is the corrected usable count?

Accepted Answer

126 host addresses. The block has 128 total addresses; exclude its network and broadcast addresses: 128 − 2 = 126.

Question 13

What is the network address of 10.46.19.203/23?

Accepted Answer

10.46.18.0. Third-octet blocks start at even values; this block covers third octets 18 and 19.

Question 14

An ordinary IPv4 LAN needs 14 interface addresses total, gateway included. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

Accepted Answer

/28. Its 16 total addresses leave 14 traditional host addresses; a /29 leaves 6.

Question 15

What is the last traditionally usable host address in the ordinary IPv4 LAN containing 192.0.2.219/29?

Accepted Answer

192.0.2.222. The block is .216–.223; .223 is broadcast, so .222 is the last host.

Question 16

Do 203.0.113.126/26 and 203.0.113.129/26 belong to the same numerical IPv4 subnet?

Accepted Answer

No. Their network addresses are 203.0.113.64 and 203.0.113.128. A shared first three octets does not settle a /26 comparison.

Question 17

A learner gives 198.51.100.192 as the broadcast for an ordinary IPv4 LAN containing 198.51.100.173/27. What is the corrected broadcast?

Accepted Answer

198.51.100.191. This block starts at .160; .192 starts the next block. Broadcast is the address immediately before that next boundary.

Question 18

What is the subnet broadcast address for an ordinary IPv4 LAN containing 172.22.35.9/23?

Accepted Answer

172.22.35.255. The block starts at 172.22.34.0 and ends just before 172.22.36.0.

Question 19

Which IPv4 CIDR prefix length matches the subnet mask 255.255.255.240?

Accepted Answer

/28. The first three octets contribute 24 one bits; 240 is 11110000, contributing four more.

Question 20

An ordinary IPv4 LAN needs 15 interface addresses in total, gateway included. Exclude growth and extra reservations. Which prefix gives the smallest address block that fits?

Accepted Answer

/27. It leaves 30 traditional host addresses. A /28 leaves 14, which is one short.

Question 21

On an ordinary IPv4 LAN, is 10.61.13.0/23 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Traditionally usable host address. This block is 10.61.12.0–10.61.13.255; .13.0 is inside it. A final .0 does not by itself identify the network address.

Question 22

A learner gives 172.24.71.255 as the last usable host in an ordinary LAN containing 172.24.70.18/23. What is the corrected last host address?

Accepted Answer

172.24.71.254. The block’s broadcast is 172.24.71.255; the last traditional host address is one before it.

Question 23

What is the network address of 192.168.47.201/22?

Accepted Answer

192.168.44.0. Third-octet boundaries are multiples of 4; 47 falls in the block covering 44–47.

Question 24

On an ordinary IPv4 LAN, is 203.0.113.184/29 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Network address. /29 boundaries advance by 8 in the fourth octet, and 184 is a multiple of 8. This block ends at .191.

Question 25

An ordinary IPv4 LAN needs addresses for 30 endpoint interfaces plus 1 gateway interface. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

Accepted Answer

/26. The demand is 30 + 1 = 31; /27 leaves only 30 traditional host addresses, while /26 leaves 62.

Question 26

What is the first traditionally usable host address in the ordinary IPv4 LAN containing 10.84.51.230/23?

Accepted Answer

10.84.50.1. The network is 10.84.50.0; this block spans third octets 50 and 51.

Question 27

A learner treats /22 as fourth-octet blocks and reports 10.73.31.0 as the network for 10.73.31.88/22. What is the corrected network address?

Accepted Answer

10.73.28.0. The mask is 255.255.252.0, so boundaries advance by 4 in the third octet; this block covers 28–31.

Question 28

An IPv4 CIDR block contains exactly 128 total addresses, before exclusions. What is its prefix length?

Accepted Answer

/25. Since 128 = 2^7, there are 7 host bits; 32 − 7 = 25 prefix bits.

Question 29

What is the subnet broadcast address for an ordinary IPv4 LAN containing 192.0.2.46/30?

Accepted Answer

192.0.2.47. The 4-address block starts at .44; the next starts at .48.

Question 30

An ordinary IPv4 LAN needs 62 interface addresses in total, including the gateway. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

Accepted Answer

/26. Its 64 total addresses leave 62 traditional host addresses; /27 leaves 30.

Question 31

Do 10.95.24.250/23 and 10.95.25.7/23 belong to the same numerical IPv4 subnet?

Accepted Answer

Yes. Both have network address 10.95.24.0; a /23 here covers third octets 24 and 25.

Question 32

What is the last traditionally usable host address in the ordinary IPv4 LAN containing 172.26.86.9/22?

Accepted Answer

172.26.87.254. The block runs from 172.26.84.0 through broadcast 172.26.87.255.

Question 33

A learner subtracts network, broadcast, and a separate gateway reservation from a /30 LAN and reports 1 usable interface address. What is the traditional usable capacity, counting a gateway as an interface?

Accepted Answer

2 interface addresses. The block has 4 total addresses. Exclude network and broadcast once; a gateway, if present, occupies one of the remaining two.

Question 34

On an ordinary IPv4 LAN, is 192.168.100.255/23 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Traditionally usable host address. The block is 192.168.100.0–192.168.101.255; its broadcast is .101.255. A final .255 alone does not identify broadcast.

Question 35

An ordinary IPv4 LAN needs 63 interface addresses in total, gateway included. Exclude growth and extra reservations. Which prefix gives the smallest address block that fits?

Accepted Answer

/25. It leaves 126 traditional host addresses. A /26 leaves 62, so it is one short.

Question 36

What is the network address of 203.0.113.233/25?

Accepted Answer

203.0.113.128. The two fourth-octet blocks start at 0 and 128; 233 is in the second.

Question 37

A learner rounds 198.51.100.107/28 up to network address 198.51.100.112. What is the corrected network address?

Accepted Answer

198.51.100.96. Network boundaries advance by 16; 107 is inside .96–.111. Choose the containing block, not the next boundary.

Question 38

On an IPv4 point-to-point link using RFC 3021, how many endpoint addresses does 10.106.8.40/31 provide?

Accepted Answer

2 endpoint addresses. They are 10.106.8.40 and 10.106.8.41. In this point-to-point context, both are endpoint addresses; do not subtract network and directed broadcast.

Question 39

An IPv4 address lies in a subnet’s traditional usable host range. Does that alone prove it is free to assign?

Accepted Answer

No. It may already be assigned or reserved by local policy. Arithmetic gives a candidate range; address management determines availability.

Question 40

An ordinary IPv4 LAN needs 254 interface addresses in total, including the gateway. With no growth allowance or extra reservations, which prefix gives the smallest address block that fits?

Accepted Answer

/24. It has 256 total addresses and 254 traditional host addresses; /25 leaves 126.

Question 41

What is the subnet broadcast address for an ordinary IPv4 LAN containing 10.117.58.177/22?

Accepted Answer

10.117.59.255. The block starts at 10.117.56.0, covers third octets 56–59, and ends just before 10.117.60.0.

Question 42

An ordinary IPv4 /27 LAN has a requirement of 30 interface addresses total, already including its gateway. A learner increases the requirement to 31. What is the corrected required interface count?

Accepted Answer

30 interface addresses. The gateway was already included. Count it once; the stated demand fits the /27 block’s 30 traditional host addresses.

Question 43

What destination address does the IPv4 host route 10.128.9.17/32 match?

Accepted Answer

10.128.9.17 only. All 32 bits are specified, so the route matches one address. It is not an ordinary multi-host LAN block.

Question 44

An ordinary IPv4 LAN needs addresses for 254 endpoint interfaces plus 1 gateway interface. Ignore growth and extra reservations. Which prefix gives the smallest address block that fits?

Accepted Answer

/23. The demand is 255; /24 leaves only 254 traditional host addresses. /23 leaves 510.

Question 45

On an ordinary IPv4 LAN, is 172.28.92.0/22 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Network address. The third octet 92 is a multiple of 4 and all host bits are zero. The block covers third octets 92–95.

Question 46

What is the first traditionally usable host address in the ordinary IPv4 LAN containing 198.51.100.154/30?

Accepted Answer

198.51.100.153. The block starts at .152; its traditional hosts are .153 and .154, with broadcast .155.

Question 47

Two IPv4 interfaces have addresses in the same numerical subnet. Does that alone prove that they can communicate?

Accepted Answer

No. Matching subnet arithmetic does not establish a working link, compatible configuration, or permitted traffic. Those require checks on the actual network.

Question 48

On an ordinary IPv4 LAN, is 192.0.2.193/26 a network address, subnet broadcast address, or traditionally usable host address?

Accepted Answer

Traditionally usable host address. The block starts at .192 and broadcasts at .255; .193 is its first traditional host address.

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IPv4 Subnetting Practice Flashcards: Boundaries & Host Ranges